1. Field of the Invention
The present invention relates to aerobic wastewater treatment systems, e.g., aerobic wastewater treatment systems and, more particularly, to a vessel assembly for use in such systems.
2. Description of Prior Art
Aerobic wastewater treatment systems are generally comprised of three main vessels, a trash or pretreatment vessel, an aeration vessel, and a pump tank. In a typical system, wastewater from a residence, industrial facility, or the like, passes into the pretreatment tank where most of the solids settle out. The effluent from the pretreatment tank then flows into the aeration vessel wherein remaining solids are subjected to aerobic digestion to provide a substantially solids-free effluent which then passes into the pump tank for discharge. It is common for the aeration vessel to include an inverted frustoconical partition disposed in the aeration vessel which effectively divides the aeration vessel into an aeration chamber and a clarifier chamber, an oxygen-containing gas being introduced into the oxygen chamber, substantially clarified water passing from the clarifier chamber into the pump tank.
While the various vessels making up the aerobic wastewater treatment system can be made of a variety of materials including concrete, fiberglass, steel, etc., many such vessels are made of composites comprised of fiberglass or similar reinforcing materials and resins, e.g., epoxy, phenolics, etc.
U.S. Pat. No. 6,358,411, incorporated herein by reference for all purposes, discloses a wastewater treatment plant comprised of two main vessels, one of the vessels having an interior partition forming a closed compartment as to the remaining interior part of the vessel. Thus, effectively there is formed a three vessel system using only the two main tanks. In the system disclosed in U.S. Pat. No. 6,358,411, one of the vessels forms an aerobic treatment chamber and in this regard contains an inverted, frustoconical partition to divide the vessel into a clarifier chamber and an aeration chamber. The other vessel, as noted above, has a compartment formed therein by means of a partition, the partition serving to form a pretreatment chamber, the remainder of the vessel forming a holding chamber or pump tank.